Dielectric element and method for fabricating the same

ABSTRACT

It is disclosed a dielectric element comprising a lower electrode, a dielectric layer, and an upper electrode which are provided on a substrate, in which at least one of the electrodes is a Pt layer, a Ru layer is used as a base layer for the Pt layer. In the fabrication of the dielectric element, the Pt layer is formed by electroplating, a photoresist pattern is used as a plating mask, and an Ru layer is formed as a seed layer. The present invention makes it possible to provide a dielectric element using Pt as an electrode material, that is capable of easily forming a Pt electrode having excellent electrical characteristics without generating voids or seams, that is capable of forming a fine pattern, and that does not occur contamination in a processing chamber, and a method for fabricating a dielectric element of having the characteristics mentioned above.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a dielectric element having alower electrode, a dielectric layer, and an upper electrode in which Ptis used as an electrode material, and a method for fabricating such adielectric element.

[0003] 2. Description of Relevant Art

[0004] In recent years, attempts have been made actively to apply adielectric element fabricated by using a high dielectric material suchas BTO, STO or BST, or by using a ferroelectric material such as SBT,SBTN or PZT to a next-generation highly integrated DRAM or non-volatilememory.

[0005] Each of the aforementioned dielectric materials is made of pluralmetal oxides. Since a process for forming a dielectric layer isperformed in an oxidative atmosphere, it is desirable to use aconductive material as an electrode material for a dielectric elementthat is not likely to be oxidized, or exhibits a conductivity even whenit is oxidized.

[0006] Those conductive materials include metals such as Pt, Ir, Ru, Rh,Re, Os, and Au, and oxides thereof. Above all, a dielectric elementusing Pt as an electrode material has been attracting attention due tothe excellent conductivity, the heat and chemical stability, the abilityto form a high dielectric thin film or a ferroelectric thin film with adesirable orientation controllability, etc.

[0007] In order to increase the degree of integration of IC circuits, itwill be desired in the future to micro-process dielectric elements onthe order of about 0.5 μm or less, particularly about 0.2 μm or less.However, the mass-production processing limit, i. e., etchingperformance, of a Pt electrode is about 0.8 μm at present, and theelectrode after the processing is likely to have a tapered ortrapezoidal shape. Thus, an increase in the degree of integration of ICcircuits using Pt still has problems to be solved.

[0008] Moreover, since it is difficult to perform etching Pt by achemical reaction with a halogen gas, Pt is generally processedphysically by a sputtering method and the like. However, the damagecaused to a dielectric layer during such a physical processing methoddeteriorates electrical characteristics of the dielectric element.

[0009] Furthermore, it takes a long time to process Pt, and Pt residuesgenerated during the processing may be adhered to an inner wall of aprocessing chamber, thereby causing contamination. Therefore, it isnecessary to clean the inside of the processing chamber and an etcherevery time when the processing is completed of several wafers.

[0010] Reports on Pt electrode materials in dielectric elements havebeen made in various articles. “Monthly Semiconductor World” (November,1998, pp. 62-67) discloses a semiconductor element where BST, a highdielectric material, is used as a dielectric layer, and Pt is used as anelectrode material. It also describes that as Pt is mostly processed byphysical sputtering method, an etched-away residue or product may beadhered to the processed Pt electrode surface, or a Pt electrode mayhave a tapered shape, thereby making it difficult to form a finepattern.

[0011] “Monthly Semiconductor World” (July, 1999, pp. 30-34) teaches amethod of forming Pt lower electrode in a contact hole on a substrate byelectroplating, where an Ru layer is provided as an electroplating seedlayer onto an entire inner surface of the contact hole, and an SiO₂ filmis used as a plating mask layer, in the fabrication of a dielectricelement having a self-aligned stacked (SAS) capacitor structure usingBST, a high dielectric material, as a dielectric layer.

[0012] In such a case, however, the Pt plated layer grows not only fromthe Ru layer on the bottom surface of the contact hole, but also fromthe Ru layer on the inner side surface of the contact hole. Therefore, acoarse plated layer having voids or seams may be resulted.

[0013] Furthermore, the SiO₂ film used as the plating mask should bedry-etched and removed by using a strong acid fluorine-based gas such asCF₄, CHF₃, or C₂F₆. Therefore, during the etching process, an insulatingfilm, generally an SiO₂ layer, on the substrate will also be strippedaway.

[0014] In order to avoid such a problem, a wet etching or removingmethod using an HF solution may be used. However, the removal effectthereof is smaller than that of by the dry etching method, and the wetetching method has the problem of a particle generation. Also, the Ruseed layer cannot be removed by the HF solution. Therefore, after theSiO₂ film as a mask is removed by the HF solution, the Ru seed layerneeds to be separately removed by dry etching. Thus, the wet etchingmethod has a poor production efficiency.

[0015] Unexamined Published Japanese Patent Application (Kokai) No.335588/1998 discloses a method for fabricating a ferroelectric elementhaving a structure where a ferroelectric substance is interposed betweenelectrodes containing a noble metal as its main component, wherein abase layer such as Pd, Ni, Ti, or TiN that catalyzes the plating of thenoble metal is firstly formed, and then the noble metal is depositedonto the base layer by a plating method to form an electrode. However,it has problems that each of the afore-mentioned materials for the baselayer loses its conductivity when oxidized by a heat treatment in theoxygen atmosphere, thereby deteriorating the conductivity of theelectrode. Moreover, it is difficult to remove the base layer made ofeach of the said materials by etching, and the material etched away maycontaminate the inside of the processing chamber.

SUMMARY OF THE INVENTION

[0016] An object of the present invention is to provide a dielectricelement using Pt as an electrode material, that is capable of easilyforming a Pt electrode having excellent electrical characteristicswithout generating voids or seams, that is capable of forming a finepattern, and that does not occur contamination in a processing chamber.

[0017] Another object of the present invention is to provide a methodfor fabricating a dielectric element of having the characteristicsmentioned above.

[0018] As a result of intensive studies made in order to solve theabove-described problems, the present inventors found out that, in theformation of a Pt electrode by electroplating, the prior art problemoccurred by the use of said strong acid material for removing a mask canbe solved by using a photoresist layer instead of the SiO₂ layer as amask for electroplating, that is capable of being removed by an oxygenplasma treatment.

[0019] Moreover, the present inventors found out that the prior artproblem of contamination occurred in the processing chamber during theremoval of the seed layer can be solved by using an Ru material, as aseed layer for forming a Pt plated layer, whose oxide exhibits aconductivity and can be easily removed by an oxygen plasma treatment.

[0020] Furthermore, the present inventors found out that the prior artproblem caused by using an SiO₂ film as a mask, and by forming an Rulayer on an entire inner surface of a contact hole as a seed layer, canbe solved by forming a photoresist pattern onto an Ru layer over asubstrate as a plating mask, and by performing Pt electroplating onto anexposed area of the Ru layer where no mask pattern is formed.

[0021] Thus, the present invention provides a dielectric element formedby sequentially depositing on a substrate an Ru layer, a Pt layer, adielectric layer which is a ferroelectric layer, and a Pt layer(hereinafter, referred to as a “first dielectric element”).

[0022] The present invention also provides a method for fabricating adielectric element (hereinafter, referred to as a “first dielectricelement fabrication method”) which comprises:

[0023] (I) forming an Ru layer on a substrate;

[0024] (II) forming a photoresist layer on the Ru layer;

[0025] (III) selectively exposing the photoresist layer, and forming aphotoresist pattern as a mask on the Ru layer;

[0026] (IV) forming a Pt layer, which is to be a lower electrode, on anexposed or unmasked area of the Ru layer by electroplating using a Ptplating solution utilizing the Ru layer as an electroplating electrode;

[0027] (V) removing the photoresist pattern and the Ru layer providedthereunder;

[0028] (VI) forming a dielectric layer on the Pt layer; and

[0029] (VII) forming a conductive layer, which is to be an upperelectrode, on the dielectric layer.

[0030] The present invention also provides a dielectric element formedby sequentially depositing on a substrate a Pt layer, a dielectriclayer, an Ru layer, and a Pt layer (hereinafter, referred to as a“second dielectric element”).

[0031] The present invention also provides a method for fabricating adielectric element (hereinafter, referred to as a “second dielectricelement fabrication method”) which comprises:

[0032] (I) forming a conductive layer, which is to be a lower electrode,on a substrate;

[0033] (II) forming a dielectric layer on the conductive layer;

[0034] (III) forming an Ru layer on the dielectric layer;

[0035] (IV) forming a photoresist layer on the Ru layer;

[0036] (v) selectively exposing the photoresist layer, and forming aphotoresist pattern as a mask on the Ru layer;

[0037] (VI) forming a Pt layer, which is to be an upper electrode, on anexposed or unmasked area of the Ru layer by electroplating using a Ptplating solution utilizing the Ru layer as an electroplating electrode;and

[0038] (VII) removing the photoresist pattern and the Ru layer providedthereunder.

[0039] The present invention also provides a dielectric element formedby sequentially depositing on a substrate an Ru layer, a Pt layer, adielectric layer, an Ru layer, and a Pt layer (hereinafter, referred toas a “third dielectric element”).

[0040] The present invention also provides a method for fabricating adielectric element (hereinafter, referred to as a “third dielectricelement fabrication method”) which comprises:

[0041] (I) forming an Ru layer on a substrate;

[0042] (II) forming a photoresist layer on the Ru layer;

[0043] (III) selectively exposing the photoresist layer, and forming aphotoresist pattern as a mask on the Ru layer;

[0044] (IV) forming a Pt layer, which is to be a lower electrode, on anexposed or unmasked area of the Ru layer by electroplating using a Ptplating solution utilizing the Ru layer as an electroplating electrode;

[0045] (V) removing the photoresist pattern and the Ru layer providedthereunder;

[0046] (VI) forming a dielectric layer on the Pt layer;

[0047] (VII) forming an Ru layer on the dielectric layer;

[0048] (VIII) forming a photoresist layer on the Ru layer;

[0049] (IX) selectively exposing the photoresist layer, and forming aphotoresist pattern as a mask on the Ru layer;

[0050] (X) forming a Pt layer, which is to be an upper electrode, on anexposed or unmasked area of the Ru layer by electroplating using a Ptplating solution utilizing the Ru layer as an electroplating electrode;and

[0051] (XI) removing the photoresist pattern and the Ru layer providedthereunder.

BRIEF DESCRIPTION OF THE DRAWINGS

[0052]FIG. 1 is a schematic cross-sectional view illustrating a step ina method for fabricating a dielectric element according to an example ofthe present invention;

[0053]FIG. 2 is a schematic cross-sectional view illustrating a step inthe method for fabricating a dielectric element according to the exampleof the present invention;

[0054]FIG. 3 is a schematic cross-sectional view illustrating a step inthe method for fabricating a dielectric element according to the exampleof the present invention;

[0055]FIG. 4 is a plan view illustrating the step illustrated in FIG. 3;

[0056]FIG. 5 is a schematic cross-sectional view illustrating a step inthe method for fabricating a dielectric element according to the exampleof the present invention;

[0057]FIG. 6 is a schematic cross-sectional view illustrating a step inthe method for fabricating a dielectric element according to the exampleof the present invention;

[0058]FIG. 7 is a schematic cross-sectional view illustrating a step inthe method for fabricating a dielectric element according to the exampleof the present invention;

[0059]FIG. 8 is a schematic cross-sectional view illustrating a step inthe method for fabricating a dielectric element according to the exampleof the present invention;

[0060]FIG. 9 is a schematic cross-sectional view illustrating a step inthe method for fabricating a dielectric element according to the exampleof the present invention;

[0061]FIG. 10 is a plan view illustrating the step illustrated in FIG.9;

[0062]FIG. 11 is a schematic cross-sectional view illustrating a step inthe method for fabricating a dielectric element according to the exampleof the present invention;

[0063]FIG. 12 is a plan view illustrating the dielectric elementobtained in the example of the present invention; and

[0064]FIG. 13 is a graph showing a hysteresis curve of the dielectricelement obtained in the example of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0065] The present invention will be specifically described below.

[0066] The “first dielectric element” of the present invention is adielectric element formed by sequentially depositing on a substrate anRu layer, a Pt layer (a lower electrode), a dielectric layer, and a Ptlayer (an upper electrode) on a substrate, wherein the dielectric layeris a ferroelectric layer.

[0067] Examples of a material for forming the ferroelectric layer usedin the first dielectric element include those containing lead containingcompounds such as PZT, PLZT and PLZTN, and those containing bismuth (Bi)layered compounds such as SBT and SBTN.

[0068] Particularly, a material for forming a Bi-based ferroelectriclayer containing a Bi layered compound has been attracting publicattention as a material for semiconductor memories and sensors becauseit has advantageous characteristics such as requiring small coercivefield in remanent polarization P-E hysteresis curve and henceexperiencing less fatigue as a result of repeated polarizationswitching.

[0069] Preferred examples of the material for forming a Bi-basedferroelectric layer include those containing a Bi alkoxide, an A metalalkoxide, where A represents at least one metallic element selected fromthe group consisting of Bi, Pb, Ba, Sr, Ca, Na, K, and rare earthmetallic elements, and a B metal alkoxide, where B represents at leastone metallic element selected from the group consisting of Ti, Nb, Ta,W, Mo, Fe, Co, and Cr.

[0070] Preferred materials for forming a Bi-based ferroelectric layerare those forming a ferroelectric layer containing a Bi layered compoundrepresented by the following general formula (I):

(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻  (I)

[0071] where A represents at least one metallic element selected fromthe group consisting of Bi, Pb, Ba, Sr, Ca, Na, K, and rare earthmetallic elements; B represents at least one metallic element selectedfrom the group consisting of Ti, Nb, Ta, W, Mo, Fe, Co, and Cr; and m isan integer of 1-5.

[0072] Among these, particularly preferred materials for forming aferroelectric layer are those such that the above-described Bi-basedferroelectric layer contains a Bi layered compound represented by thefollowing general formula (II):

Sr_(1−x)Bi_(2+y)(Ta_(2−z),Nb_(z))O_(9+α)  (II)

[0073] where 0≦x, y and α, independently <1 ; 0≦z<2.

[0074] In the present invention, it is particularly preferred that atleast two different metal alkoxides selected from the group consistingof the A metal alkoxide, the B metal alkoxide, and the Bi alkoxide forma composite metal alkoxide. By forming a composite material from two ormore different metal alkoxides, it is possible to inhibit separation(segregation) of a single metallic element and burnout thereof.Therefore, it is possible to inhibit the generation of a leakage currentmore effectively.

[0075] The metal alkoxides contained in the aforesaid materials forforming a Bi-based ferroelectric layer are exemplified as the followingspecific embodiments (a)-(e):

[0076] (a) A-Bi composite metal alkoxide and B metal alkoxide;

[0077] (b) Bi—B composite metal alkoxide and A metal alkoxide;

[0078] (c) A-B composite metal alkoxide and Bi metal alkoxide;

[0079] (d) A-Bi—B composite metal alkoxide; and

[0080] (e) A metal alkoxide, B metal alkoxide, and Bi alkoxide.

[0081] The composite metal alkoxide as used hereabove is a compoundobtainable by reacting different metal alkoxides within a solvent at atemperature in a range from 20 to 100° C. for about 2 to 15 hours.Toward the end point of reaction, the liquid is gradually discolored tofinally become a dark brown liquid. A point in time when the liquid hasbeen discolored completely may be regarded as the end point of thereaction. The thus obtained composite metal alkoxide is considered to beone defined in the “Manufacturing Method of Glass Ceramics by Sol-GelProcess and Applications” (Applied Tech. Pub. Co., Jun. 4, 1989),pp.46-47, and to be expressed specifically by: ABi(OR¹)_(k)(OR²)₃,BBi(OR³)_(n)(OR²)₃, AB(OR¹)_(k)(OR³)_(n), ABBi(OR¹)_(k)(OR³)_(n)(OR²)₃,where A and B are as defined hereabove; k is a valency of metallicelement A; n is a valency of metallic element B; and R¹, R², and R³respectively represent alkyl groups having 1-6 carbon atomsindependently of each other. Among these, it is preferable to useABi(OR¹)_(k)(OR²)₃, BBi(OR³)_(n)(OR²)₃, or ABBi(OR¹)_(k)(OR³)_(n)(OR²)₃,which is a composite compound of Bi said to have a high sublimation,i.e., the above-described embodiment (a), (b), or (d).

[0082] In the present invention, the aforesaid material for forming aBi-based ferroelectric layer is preferably a sol-gel liquid obtainedthrough hydrolysis and partial polycondensation using water alone, orwater and a catalyst.

[0083] Further, the material for forming a Bi-based ferroelectric layerpreferably contains a product obtainable by reacting the above-describedcomposite metal alkoxide with at least one compound (stabilizer)selected from the group consisting of carboxylic anhydrides,dicarboxylic acid mono-esters, β-diketones, and glycols.

[0084] Both of the hydrolysis and partial polycondensation and thereaction with the stabilizer may be used.

[0085] More specifically, preferred examples include:

[0086] (1) an embodiment where the material for forming a Bi-basedferroelectric layer is subjected to the hydrolysis and partialpolycondensation using water alone, or water and a catalyst to obtain asol-gel liquid;

[0087] (2) an embodiment where the material for forming a Bi-basedferroelectric layer is subjected to the hydrolysis and partialpolycondensation using water alone, or water and a catalyst to obtain asol-gel liquid, and then a stabilizer is added thereto to react with thecomposite metal alkoxide in the liquid;

[0088] (3) an embodiment where the composite metal alkoxide is reactedwith the stabilizer; and

[0089] (4) an embodiment where the composite metal alkoxide in thematerial for forming a Bi-based ferroelectric layer is reacted with thestabilizer, and then the material for forming a Bi-based ferroelectriclayer is subjected to the hydrolysis and partial polycondensation usingwater alone, or water and a catalyst to obtain a sol-gel liquid.

[0090] The aforementioned stabilizer is used for improving thepreservation stability of the coating solution, and particularly usedfor inhibiting the thickening and gelling of the coating solution afterit is subjected to the hydrolysis process. Each of the stabilizersmentioned above is preferably one with a short chain having 1-6 carbonatoms in view of improving the polarity of the metallic compound andenhancing its inorganic properties after the application. Lowermonocarboxylic acids such as acetic acid, propionic acid, butyric acid,and valeric acid can be used as stabilizers if desired.

[0091] In the case where the material for forming a Bi-basedferroelectric layer is subjected to hydrolysis and partialpolycondensation, the hydrolysis and partial polycondensation reactionsare conducted by adding water alone, or water and a catalyst into thecoating solution, and then stirred at 20 to 50° C. for several hours toseveral days. Any catalysts such as metal alkoxides that are known inthe art of hydrolysis may be employed and exemplary catalysts includeacid catalysts such as inorganic acids including, for example,hydrochloric acid, sulfuric acid and nitric acid; and organic acids suchas acetic acid, propionic acid and butyric acid; and inorganic ororganic alkali catalysts such as sodium hydroxide, potassium hydroxide,ammonia, monoethanolamine, diethanolamine, and tetramethylammoniumhydroxide. Among these, acid catalysts are particularly preferable inview of the properties of the formed film.

[0092] The composite metal alkoxide is reacted with a stabilizer asdescribed above for carboxylation, β-diketonization, chelation, etc., sothat it is possible to obtain a product (organometallic compound) havinga polarity and an excellent stability. Moreover, the hydrolyzabilitythereof is improved, and practical application of a polar solvent can berealized. Consequently, it is possible to sufficiently facilitate thecondensation polymerization reaction by the sol-gel process in thecoating solution. Furthermore, by the generation of an inorganic bond(methalloxane bond) such as Bi—O—Bi, Bi—O—Ta, Bi—O—Sr, or Ta—O—Bi—O—Sr,it is possible to reduce the separation (segregation) and burnoutamounts of a specific metallic element such as Bi, and to enhance theinorganicity of the coating solution.

[0093] Examples of solvents for the coating solution for forming aBi-based ferroelectric layer include saturated aliphatic solvents,aromatic solvents, alcoholic solvents, glycol-based solvents,ether-based solvents, ketone-based solvents, and ester-based solvents.Among these, alcoholic solvents, glycol-based solvents, ether-basedsolvents, ketone-based solvents, and ester-based solvents, which haveoxygen atoms in the molecules, are preferably used when hydrolysis typesol-gel liquids are prepared.

[0094] The ferroelectric layer can be formed by using known applicationmethod such as an LSMCD (=liquid source misted chemical deposition)method, a spinner method, or a dip method. The thickness of theferroelectric layer is preferably in a range from about 40 to 300 nm.

[0095] The Ru layer is preferably made of Ru and/or an Ru oxide(RuO_(x)). More specifically, the Ru layer is preferably one selectedfrom a layer made of Ru, a layer made of RuO_(x), a layer containing Ruand RuO_(x), and a layer formed by sequentially depositing the layermade of Ru and the layer made of RuO_(x).

[0096] The method for forming the Ru layer is not limited to anyparticular method. The Ru layer can be formed by various methodsincluding an electroless plating method, a sputtering method, a vapordeposition method, a CVD method, and a coating method. The thickness ofthe Ru layer is preferably in a range from about 10 to 500 nm in view ofthe conductivity, the processing cost, the micro-processing, and thelike.

[0097] Pt forming the lower electrode and the upper electrode has anexcellent conductivity, and heat and chemical stability. Moreover, whena high dielectric layer or a ferroelectric layer is used as a dielectriclayer, it is possible to form a dielectric substance with a desirableorientation controllability. Therefore, a dense ferroelectric layer withan excellent orientation controllability can be obtained in the presentinvention. In the first dielectric element, although the method forforming the Pt layer is not limited to any particular method, the Ptlayer is preferably formed by electroplating using a Pt platingsolution. The thickness of each of the lower electrode and the upperelectrode is preferably in a range from about 50 to 300 nm.

[0098] In the first dielectric element, the Ru layer is provided as abase layer of the Pt layer which serves as the lower electrode.Therefore, when the Pt layer is formed by electroplating, the Ru layercan function as a seed layer for forming a Pt plated layer as Ru andRuO_(x), are conductive materials. Furthermore, as the Ru layer becomesvolatile RuO₄ (melting point: 25° C., boiling point: 40° C.) by anoxygen-containing plasma treatment at a temperature of 108° C. orhigher, the inside of the processing chamber is not contaminated byresidues, during removing it.

[0099] The Ru layer remained under the Pt electrode functions as anelectrode material together with the Pt electrode, thereby making itpossible to improve the electrical characteristics of the dielectricelement.

[0100] The “first dielectric element fabrication method” of the presentinvention comprises:

[0101] (I) forming an Ru layer on a substrate;

[0102] (II) forming a photoresist layer on the Ru layer;

[0103] (III) selectively exposing the photoresist layer, and forming aphotoresist pattern as a mask on the Ru layer;

[0104] (IV) forming a Pt layer, which is to be a lower electrode, on anexposed or unmasked of the Ru layer by electroplating using a Pt platingsolution utilizing the Ru layer as an electroplating electrode;

[0105] (V) removing the photoresist pattern and the Ru layer providedthereunder;

[0106] (VI) forming a dielectric layer on the Pt layer; and

[0107] (VII) forming a conductive layer, which is to be an upperelectrode, on the dielectric layer.

[0108] The formation of the Ru layer in the above-described step (I) canbe performed by the same material and method as those described above inthe description of the “first dielectric element”.

[0109] The formation of the photoresist layer in the above-describedstep (II) can be performed, for example, by applying a photoresistcomposition used for fabricating a printed board, a semiconductorintegrated circuit, etc., on the Ru layer, and drying the photoresistcomposition.

[0110] Generally known photoresist compositions include those that canform pattern of a positive image or a negative image after a developmentprocess by irradiation of radiations or electron beams. If theirradiated portion of a photoresist composition becomes soluble in adeveloping solution and a positive image is thus provided, such acomposition is referred to as a positive photoresist composition. If theirradiated portion of a photoresist composition becomes insoluble in adeveloping solution and a negative image is thus provided, such acomposition is referred to as a negative photoresist composition.

[0111] Also known are photoresist compositions which can form aphotoresist pattern, without performing the development process, byusing radiation or electron beam irradiation to decompose and remove theirradiated portion. It is possible to employ such compositions in thepresent invention.

[0112] When forming a photoresist layer in the “first fabricationmethod” of the present invention, it is possible to employ any one ofthe aforementioned photoresist compositions. However, it is desirablethat the photoresist composition has a sufficient resistance against theplating solution, and can form a minute pattern on the order of

[0113]0.5 μm or less with a good reproducibility. A positive photoresistcomposition containing novolac resin and a quinone diazide groupcontaining compound is preferably used as such a photoresistcomposition.

[0114] Upon forming the photoresist pattern in the above-described step(III), the exposure conditions can be suitably selected according to aphotoresist used. The exposure is performed by exposing the photoresistlayer through a desired mask pattern using, for example, a light sourcewhich emits active beams such as ultraviolet rays, far ultraviolet rays,excimer laser, X-rays, and electron beams (e.g., a low-pressure mercurylamp, a high-pressure mercury lamp, an extra-high pressure mercury lamp,a xenon lamp, etc.), or by scanning the photoresist layer with electronbeams. Thereafter, post-exposure bake is conducted as needed.

[0115] In the case of using a photoresist that requires a developmentfor forming a pattern after the exposure, the development is not limitedto any particular method. For example, it is possible to conduct a dipdevelopment in which a substrate with a photoresist coated thereon isdipped in a developing solution for a certain period of time, and thenthe substrate is washed with water and dried; a paddle development inwhich a developing solution is dripped onto the surface of the appliedphotoresist and left standing for a certain period of time, and thephotoresist is washed with water and dried; a spray development in whicha developing solution is sprayed to the surface of the photoresist, andthe photoresist is washed with water and dried; or the like. A desiredphotoresist pattern can thusly be formed.

[0116] In the above-described step (IV), the Pt layer which is to be alower electrode is formed by the electroplating process using a Ptplating solution on the area of the Ru layer which is not masked by thephotoresist pattern formed in step (III). The unmasked Ru layer is usedas an electroplating electrode (seed layer).

[0117] As the Pt plating solution, “Platanex 3LS” (product ofElectroplating Engineers of Japan, Ltd.) which is a strong acid Ptplating solution of pH of about 1, for example, can be used.

[0118] The formation of the Pt lower electrode using the electroplatingmethod can be performed by making the substrate in contact with the Ptplating solution for about 1 to 20 minutes utilizing the Ru layer as theelectroplating electrode under such conditions that the current densityis 1×10⁵ A/m²(=1A/dcm²) and the Pt plating solution bath temperature isin a range from about 70 to 90° C.

[0119] As the electroplating apparatus, an apparatus as described in“Monthly Semiconductor World” (January, 1998, pp. 58-63) can be used.

[0120] By forming the Pt lower electrode by electroplating, the step ofetching the Pt electrode can be omitted. Therefore, the problem causedby the etching processing is solved, and the formation of a minutepattern, a reduction in a damage to the dielectric layer, and animproved production efficiency are realized. Furthremore, as two steps,i.e., the step of forming the lower electrode and the step of etchingprocessing, can be replaced by one plating step, the present inventionhas an excellent mass-productivity.

[0121] Moreover, since the Ru layer becomes volatile RuO₄ by anoxygen-containing plasma treatment at a temperature of 108° C. orhigher, the photoresist layer and the Ru layer forming the base layer ofthe photoresist layer can be simultaneously removed easily withoutcontaminating the inside of the processing chamber. Since the Ru layerremained under the Pt electrode functions as an electrode materialtogether with the Pt electrode, the electrical characteristics of thedielectric element can be improved.

[0122] Furthermore, unlike the conventional example in which the Rulayer is formed on the entire inner surface of the contact hole using anSiO₂ film as a plating mask to form the Pt plated layer in the contacthole, it becomes possible to selectively deposit the plating onto the Rulayer provided on the substrate precisely in accordance with the maskpattern by forming the photoresist pattern which functions as anelectroplating mask on the Ru layer provided on the substrate. Thus, itis possible to solve the problem in the prior art that a coarse platedlayer having voids or seams is likely to be obtained.

[0123] In the above-described step (V), examples of the method forremoving the photoresist pattern and the Ru layer provided thereunderinclude a wet removing method using a stripping solution, a dry removingmethod using an oxygen-containing plasma treatment, and the like. In thepresent invention, it is preferable to use the dry removing method asthe simultaneous removal of the photoresist layer and the Ru layerprovided thereunder can simplify the fabrication steps. The dry removalmethod is preferably conducted using an oxygen-containing plasma at atemperature of 108° C. or higher, particularly in a range from 108 to450° C., in consideration of the removal of the Ru layer as the baselayer. Since the Ru layer becomes volatile RuO₄ under such a condition,it is possible to easily remove the photoresist layer and the Ru layerprovided thereunder together without contaminating the inside of theprocessing chamber.

[0124] In the above-described step (VI) of the fabrication method of thepresent invention, a high dielectric material such as STO or BST, or aferroelectric material such as SBT or PZT can be preferably used for thedielectric layer, and the Bi-based ferroelectric described in thedescription of the “first dielectric element” is particularly preferredto use for the dielectric layer, although materials for the dielectriclayer are not limited thereto. The dielectric layer can be formed byusing a known application method such as an LSMCD method, a spinnermethod, or a dip method.

[0125] In the above-described step (VII), the conductive layer which isto be an upper electrode is formed on the dielectric layer. According tothe first fabrication method of the present invention, a material forthe upper electrode is not limited to any particular material as long asit is a conductive material which is rarely oxidized, or a materialwhich exhibits a conductivity even when oxidized.

[0126] Examples of such conductive materials include metals such as Pt,Ir, Ru, Rh, Re, Os, and Au, and oxides thereof. Among these, Pt ispreferable to use due to its excellent conductivity and heat andchemical stability. Moreover, Pt is preferably used in a dielectricelement which employs a BST-based high dielectric film, or PZT orSBT-based ferroelectric film since it can form such a dielectric filmwith an excellent orientation controllability.

[0127] The electrode can be formed by using various methods such as asputtering method, a vapor deposition method, a CVD method, a coatingmethod, and an electroplating method utilizing these electrode materialsas above. In the case where Pt is used as the material for the upperelectrode, the electrode may be preferably formed by an electroplatingmethod. The electroplating method used in such a case may be the samemethod as that used when forming the lower electrode (Pt).

[0128] It is desirable to perform a heat treatment after the formationof the upper electrode to improve the contact property (conductivity)between the dielectric layer and the upper electrode.

[0129] Due to this heat treatment, crystal grains are grown, and theinterface between the dielectric thin film and the upper electrode isstabilized, thereby improving electrical characteristics of thedielectric element.

[0130] The heat treatment is preferably performed in a temperature rangeof less than 900° C., and more particularly in a temperature range fromabout 400 to 800° C. If the treatment temperature is less than 400° C.,it is difficult to sufficiently improve the aforementioned contactproperty even if the heat treatment is performed for a long time. If thetreatment temperature is equal to or higher than 900° C., the influenceof the degradation in the element characteristics due to the heat isincreased. Therefore, the treatment temperature of less than 400° C. andthat of 900° C. or higher are not preferable. The heating time ispreferably in a range from about 10 to 60 minutes. The heat treatmentatmosphere may be either the oxygen atmosphere or the inert gasatmosphere.

[0131] The “second dielectric element” of the present invention is adielectric element formed by sequentially depositing on a substrate a Ptlayer (lower electrode), a dielectric layer, an Ru layer, and a Pt layer(upper electrode).

[0132] The Ru layer, the Pt layer, and methods for forming these layersmay be the same as those described in the description of the “firstdielectric element”.

[0133] A high dielectric material such as STO or BST, or a ferroelectricmaterial such as SBT or PZT can be preferably used as the dielectriclayer, although materials for the dielectric layer are not limitedthereto. The Bi-based ferroelectric same as that used in the “firstdielectric element” is particularly preferable to use. The dielectriclayer can be formed by using a known application method such as an LSMCDmothod, a spinner method, or a dip method.

[0134] In the “second dielectric element”, the upper electrode (Ptlayer) is not directly formed on the dielectric layer, but the upperelectrode is deposited on the dielectric layer via the Ru layer. In theprior art where the upper electrode is directly formed onto thedielectric layer using, e.g., a sputtering method, a vapor depositionmethod, or a CVD method, a degradation in the dielectric characteristicsoccurs due to the reduction of the dielectric layer. In the presentinvention, however, as the Pt layer (upper electrode) is deposited viathe Ru layer over the dielectric layer, the said degradation phenomenoncan be inhibited.

[0135] Moreover, since the Ru layer is formed as a base layer for the Ptlayer (upper electrode), in the case where the Pt layer is formed byelectroplating, the Ru layer can function as a seed layer for forming aPt plated layer. As the Ru layer becomes volatile RuO₄ by anoxygen-containing plasma treatment at a temperature of 108° C. orhigher, the inside of the processing chamber is not contaminated byresidues, or the like, during removing it.

[0136] Furthermore, the Ru layer functions as an electrode materialtogether with the Pt electrode, thereby making it possible to improvethe electrical characteristics of the dielectric element.

[0137] The “second dielectric element fabrication method” comprises:

[0138] (I) forming a conductive layer, which is to be a lower electrode,on a substrate;

[0139] (II) forming a dielectric layer on the conductive layer;

[0140] (III) forming an Ru layer on the dielectric layer;

[0141] (IV) forming a photoresist layer on the Ru layer;

[0142] (V) selectively exposing the photoresist layer, and forming aphotoresist pattern as a mask on the Ru layer;

[0143] (VI) forming a Pt layer, which is to be an upper electrode, on anexposed or unmasked area of the Ru layer by electroplating using a Ptplating solution utilizing the Ru layer as an electroplating electrode;and

[0144] (VII) removing the photoresist pattern and the Ru layer providedthereunder.

[0145] In the second dielectric element fabrication method, any materialcan be used as long as it is a conductive material which is rarelyoxidized, or a material which exhibits a conductivity even whenoxidized.

[0146] Examples of such conductive materials include metals such as Pt,Ir, Ru, Rh, Re, Os and Au, and oxides thereof. Among these, Pt ispreferable to use due to its excellent conductivity and heat andchemical stability. Moreover, Pt is preferably used in a dielectricelement which employs a BST-based high dielectric film, or PZT orSBT-based ferroelectric film since it can form such a dielectric filmwith an excellent orientation controllability.

[0147] The electrode can be formed by using various methods such as asputtering method, a vapor deposition method, a CVD method, a coatingmethod, and an electroplating method utilizing the above-mentionedelectrode materials. In the case where Pt is used as the material forthe lower electrode, the electrode is preferably formed by anelectroplating method. The electroplating method used in such a case maybe the same as that used when forming the lower electrode (Pt) describedin the description of the “first dielectric element fabrication method”.

[0148] It is desirable to perform a heat treatment after the formationof the lower electrode to improve the contact property (conductivity)between the Ru layer, which is the base layer, and the lower electrode.

[0149] Unlike the conventional example in which the Ru layer is formedon the entire inner surface of the contact hole using an SiO₂ film as aplating mask to form the Pt plated layer in the contact hole, “thesecond dielectric element fabrication method” makes it possible toselectively deposit the plating onto the Ru layer provided on thesubstrate precisely in accordance with the mask pattern by using thephotoresist layer, which can be removed by an oxygen plasma treatment,as an electroplating mask when the Pt electrode serving as the upperelectrode is formed by the electroplating method. Thus, it is possibleto solve the problem in the prior art that a coarse plated layer havingvoids or seams is likely to be obtained.

[0150] Moreover, the problem in the prior art that the contamination inthe processing chamber occurs during removing a seed layer (basematerial) can be solved by using an Ru material whose oxide exhibits aconductivity and which can be easily removed by an oxygen plasmatreatment, as the seed layer for forming the Pt plated layer.

[0151] Furthermore, in the “second dielectric element fabricationmethod”, the upper electrode is provided on the dielectric layer notdirectly but via the Ru layer. In the prior art where the upperelectrode is directly formed on the dielectric layer, a degradation inthe dielectric characteristics occurs due to the reduction of thedielectric layer. According to the present invention, however, as the Ptlayer (upper electrode) is deposited via the Ru layer over thedielectric layer, the aforementioned degradation phenomenon can beinhibited.

[0152] The Ru layer functions as an electrode material together with thePt upper electrode, thereby making it possible to improve the electricalcharacteristics of the dielectric element.

[0153] The “third dielectric element” of the present invention is adielectric element formed by sequentially depositing on a substrate anRu layer, a Pt layer, a dielectric layer, an Ru layer, and a Pt layer.

[0154] In the third dielectric element, both of the lower electrode (Ptlayer) and the upper electrode (Pt layer) are formed on the Ru layer.The third dielectric element has both advantages of the aforementionedfirst and second dielectric elements.

[0155] A high dielectric material such as STO or BST, or a ferroelectricmaterial such as SBT or PZT can be preferably used as the dielectriclayer, although materials for the dielectric layer are not limitedthereto. The Bi-based ferroelectric same as that used in the “firstdielectric element” is particularly preferable to use. The dielectriclayer can be formed by using a known application method such as an LSMCDmethod, a spinner method, or a dip method.

[0156] The methods for forming the Ru layer and the Pt layer, and thelike, may be the same as those described in the first and seconddielectric elements.

[0157] The “third dielectric element fabrication method” of the presentinvention comprises:

[0158] (I) forming an Ru layer on a substrate;

[0159] (II) forming a photoresist layer on the Ru layer;

[0160] (III) selectively exposing the photoresist layer, and forming aphotoresist pattern as a mask on the Ru layer;

[0161] (IV) forming a Pt layer, which is to be a lower electrode, on anexposed or unmasked area of the Ru layer by electroplating using a Ptplating solution utilizing the Ru layer as an electroplating electrode;

[0162] (V) removing the photoresist pattern and the Ru layer providedthereunder;

[0163] (VI) forming a dielectric layer on the Pt layer;

[0164] (VII) forming an Ru layer on the dielectric layer;

[0165] (VIII) forming a photoresist layer on the Ru layer;

[0166] (IX) selectively exposing the photoresist layer, and forming aphotoresist pattern as a mask on the Ru layer;

[0167] (X) forming a Pt layer, which is to be an upper electrode, on anexposed or unmasked area of the Ru by electroplating using a Pt platingsolution utilizing the Ru layer as an electroplating electrode; and

[0168] (XI) removing the photoresist pattern and the Ru layer providedthereunder.

[0169] The third dielectric element fabrication method has theaforementioned advantages of the first and second dielectric elementfabrication methods. Each step of the third dielectric elementfabrication method can be performed in the same manner as in thecorresponding step of the first or second dielectric element fabricationmethod.

[0170] It is desirable to perform a heat treatment after the formationof the upper electrode to improve the contact property (conductivity)between the Ru layer, which is the base layer, and the upper electrode.

[0171] According to each of the above-described elements and elementfabrication methods of the present invention, even when at least one ofthe upper electrode and the lower electrode is a Pt electrode, and evenin a micro element whose processing dimensions (width, line width,diameter, etc.) are on the order of 0.5 μm or less, it is possible toobtain a dielectric element having an excellent processability andexcellent electrical characteristics without generating voids or seams.

[0172] The present invention will be described below in more detail withreference to the accompanying drawings by way of an example in which aBi-based ferroelectric thin film is used as a dielectric layer. However,the present invention is not limited to such an example. The amount ofeach component is expressed by a percentage by weight unless indicatedotherwise.

PREPARATION EXAMPLE

[0173] (Preparation of a Coating Solution For Forming Bi-BasedFerroelectric Thin Film)

[0174] A metal piece of Sr was added to a methoxyethanol (CH₃OC₂H₄OH)solution in a small amount at a time, and stirred, thereby preparing anSr alkoxide solution (Sr(OC₂H₄OCH₃)₂).

[0175] Bi(OC₂H₄OCH₃)₃ and Ta(OC₂H₅)₅ were added to the Sr alkoxidesolution, and subjected to a reflux process at a temperature of 80° C.for 20 hours, thereby preparing a coating solution for forming aBi-based ferroelectric thin film which is a composite of Sr alkoxide, Bialkoxide and Ta alkoxide.

EXAMPLE 1

[0176] As illustrated in FIG. 1, an Ru layer 3 with a thickness of 50 nmwas formed by sputtering on a Si substrate 1 of a 6-inch diameter onwhich an SiO₂ film 2 having a thickness of 100 nm was provided.

[0177] Then, as illustrated in FIG. 2, a photoresist layer 4 having athickness of 800 nm was formed onto the surface of the Ru layer 3entirely using i-line positive photoresist coating solution “TDMR-AR80”(product of Tokyo Ohka Kogyo Co., Ltd.). The photoresist layer 4 wasselectively exposed through a mask (not shown) for an exposure time of200 msec. As the exposure apparatus, the i-line stepper “NSR-2205il4E”(Nikon Corp.) was used.

[0178] After the exposure, a development process was performed using2.38 wt % of tetramethylammonium hydroxide (TMAH) aqueous solution.Next, the photoresist layer 4 was washed with water, dried, and thensubjected to a vacuum UV process and a hard bake process at atemperature of 180° C. for 3 minutes. As a result, a hole pattern 5(FIG. 3) having a diameter of 0.5 μm (represented by “d” in FIG. 3) wasformed on the Ru layer 3. The plan view illustrating the hole pattern isshown in FIG. 4.

[0179] The surface of the substrate where the hole pattern 5 was formedwas made in contact with “Platanex 3LS” (product of ElectroplatingEngineers of Japan Ltd.), which is an acid Pt plating solution, for 3minutes at a current density of 1×10⁵ A/m² and a Pt plating solutionbath temperature of 80° C. The substrate was then washed with water anddried, and a Pt layer 7 with a thickness of 200 nm was selectivelyformed on an area of the Ru layer 3 which is not covered with thephotoresist layer 4 (FIG. 5).

[0180] Next, the photoresist layer 4 and areas of the Ru layer 3 coveredwith the photoresist layer 4 were processed using a single waferprocessing type ashing apparatus “TCA-4802” (product of Tokyo Ohka KogyoCo., Ltd.) for 3 minutes under such conditions that the output frequencywas 13.56 MHz; the output power was 1000 W; the oxygen flow rate was 30sccm (flow rate of 30 cc/min.); the substrate stage temperature was 200°C.; and the pressure in the processing chamber was 60 mTorr, therebyremoving the photoresist layer 4 and the portions of the Ru layer 3 fromthe substrate 1 (FIG. 6).

[0181] Thereafter, the surface of the substrate 1 was washed with a 10wt % hydrochloric acid aqueous solution, and then washed with purewater. When the surface of the substrate 1 was observed using the SEMmicrograph thereof, a physical damage to the SiO₂ film 2 was not found,and Ru residues were also not found.

[0182] In order to improve contact between the Ru layer 3 and the Ptlayer 7, an annealing process was conducted thereto in the nitrogenatmosphere at a temperature of 600° C. for 30 minutes. Thereafter, usinga spin coater, the coating solution for forming a Bi-based ferroelectricthin film prepared in the above-described preparation example wasapplied to the structure at 2000 rpm. The thusly obtained structure wasdried for 30 minutes at a temperature of 150° C., and subjected to aheat treatment (first heat treatment) for 60 minutes at a temperature of450° C. and then to a heat treatment (second heat treatment) for 60minutes at a temperature of 750° C. in the oxygen atmosphere.

[0183] The series of steps from the application process to the secondheat treatment were repeated four times, thereby forming a Bi-basedferroelectric thin film 8 having a thickness of 200 nm (FIG. 7).

[0184] Next, an Ru layer 9 with a thickness of 50 nm was formed by asputtering method on the substrate 1 on which the Bi-based ferroelectricthin film 8 was formed (FIG. 8).

[0185] A photoresist layer 10 having a thickness of 800 nm was formed onthe entire surface of the Ru layer 9 using the aforementioned i-linepositive photoresist coating solution. The photoresist layer 10 wasselectively exposed through a mask (not shown) for an exposure time of200 msec. The mask used herein was one having a mask pattern obtained byrotating the mask pattern by an angle of 90° of the mask that has beenused in the previous process step.

[0186] After the exposure, a development process was performed using2.38 wt % of TMAH aqueous solution. Next, the photoresist layer 10 waswashed with water, dried, and then subjected to a vacuum UV process anda hard bake process at a temperature of 180° C. for 3 minutes. As aresult, a hole pattern 11 (FIG. 9) having a diameter of 0.5 μm(represented by “d” in FIG. 9) was formed above the Ru layer 3. The planview illustrating the hole pattern is shown in FIG. 10.

[0187] The surface of the substrate where the hole pattern 11 was formedwas subjected to the electroplating process under the same conditions asthose described above, thereby selectively forming a Pt layer 12 havinga thickness of 200 nm on an area of the Ru layer 9 being not coveredwith the photoresist layer 10.

[0188] Next, the photoresist layer 10 and areas of the Ru layer 9covered with the photoresist layer 10 were removed by ashing from thesubstrate in the same manner as that described above.

[0189] Thereafter, the substrate surface was washed with a 10 wt %hydrochloric acid aqueous solution, and then washed with pure water.Next, when the substrate surface was observed using the SEM micrographthereof, a physical damage to the Bi-based ferroelectric thin film wasnot found, and Ru residues were also not found.

[0190] In order to improve contact between the Ru layer 9 and the Ptlayer 12, an annealing process was conducted thereto in the nitrogenatmosphere at a temperature of 600° C. for 30 minutes, and thus, adielectric element 20 (FIG. 11) was formed. The “d” (=0.5 μm) in FIG. 11represents the width (processing dimension) of the dielectric element.

[0191] When the cross section of the dielectric element 20 was observedby the SEM micrograph thereof, it was confirmed that each of the lowerand upper electrodes had a fine structure having no voids.

[0192] In order to evaluate electrical characteristics of thethus-formed dielectric element 20, rubber-based negative photoresist“ORM-85II” (product of Tokyo Ohka Kogyo Co., Ltd.) was used to form aphotoresist pattern on the Bi-based ferroelectric thin film 8. TheBi-based ferroelectric thin film on a Pt lower electrode padcorresponding to an electrical characteristics measurement terminalsection (pad) was etched away using an etching liquid(HNO₃:HF:H₂O=7:3:40 (weight ratio)). Thereafter, the photoresist patternwas removed to expose the Pt lower electrode pad (dimension:length×width=50 μm×50 μm). The plan view illustrating such a state isshown in FIG. 12.

[0193] After performing a heat treatment in the oxygen atmosphere at atemperature of 500° C. for 30 minutes, electrical circuits were formedin the Pt lower electrode pad and the Pt upper electrode pad. Next,polarization characteristics of the dielectric element were examined. Asa result, a hysteresis curve shown in FIG. 13 was obtained, and thedielectric element had satisfactory polarization characteristics.

[0194] As described above in detail, according to the present invention,there are provided a dielectric element and a method for fabricating adielectric element such that: it is possible to easily form a Ptelectrode having excellent electrical characteristics without generatingvoids or seams; contamination in a processing chamber, or the like, doesnot occur; and it is possible to form a minute pattern.

What is claimed is:
 1. A dielectric element comprising an Ru layer, a Ptlayer, a dielectric layer, and a Pt layer, which are sequentiallydeposited on a substrate, wherein the dielectric layer is aferroelectric layer.
 2. The dielectric element according to claim 1,wherein the ferroelectric layer is formed by using a coating solutionfor forming a Bi-based ferroelectric layer containing a Bi alkoxide, anA metal alkoxide, where A represents at least one metallic elementselected from the group consisting of Bi, Pb, Ba, Sr, Ca, Na, K, andrare earth metallic elements, and a B metal alkoxide, where B representsat least one metallic element selected from the group consisting of Ti,Nb, Ta, W, Mo, Fe, Co, and Cr.
 3. The dielectric element according toclaim 2, wherein the coating solution for forming a Bi-basedferroelectric layer is a coating solution for forming a ferroelectriclayer containing a Bi layered compound represented by the followinggeneral formula (I): (Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻  (I) where Arepresents at least one metallic element selected from the groupconsisting of Bi, Pb, Ba, Sr, Ca, Na, K, and rare earth metallicelements; B represents at least one metallic element selected from thegroup consisting of Ti, Nb, Ta, W, Mo, Fe, Co, and Cr; and m is aninteger of 1-5.
 4. The dielectric element according to claim 2, whereinthe coating solution for forming a Bi-based ferroelectric layer is acoating solution for forming a ferroelectric layer containing a Bilayered compound represented by the following general formula (II):Sr_(1−x)Bi_(2+y)(Ta_(2−z),Nb_(z))O_(9+α)  (II) where 0≦x, y and α,independently <1 ; 0≦z<2.
 5. The dielectric element according to claim1, wherein a processing dimension of the element is 0.5 μm or less.
 6. Amethod for fabricating a dielectric element, comprising: (I) forming anRu layer on a substrate; (II) forming a photoresist layer on the Rulayer; (III) selectively exposing the photoresist layer, and forming aphotoresist pattern as a mask on the Ru layer; (IV) forming a Pt layer,which is to be a lower electrode, on an exposed or unmasked area of theRu layer by electroplating using a Pt plating solution utilizing the Rulayer as an electroplating electrode; (V) removing the photoresistpattern and the Ru layer provided thereunder; (VI) forming a dielectriclayer on the Pt layer; and (VII) forming a conductive layer, which is tobe an upper electrode, on the dielectric layer.
 7. The method forfabricating a dielectric element according to claim 6, wherein theconductive layer (upper electrode) in the step (VII) is a Pt layer. 8.The method for fabricating a dielectric element according to claim 7,wherein the Pt layer is formed by an electroplating method.
 9. Adielectric element comprising a Pt layer, a dielectric layer, an Rulayer, and a Pt layer, which are sequentially deposited on a substrate.10. The dielectric element according to claim 9, wherein a processingdimension of the element is 0.5 μm or less.
 11. A method for fabricatinga dielectric element, comprising: (I) forming a conductive layer, whichis to be a lower electrode, on a substrate; (II) forming a dielectriclayer on the conductive layer; (III) forming an Ru layer on thedielectric layer; (IV) forming a photoresist layer on the Ru layer; (V)selectively exposing the photoresist layer, and forming a photoresistpattern as a mask on the Ru layer; (VI) forming a Pt layer, which is tobe an upper electrode, on an exposed or unmasked area of the Ru layer byelectroplating using a Pt plating solution utilizing the Ru layer as anelectroplating electrode; and (VII) removing the photoresist pattern andthe Ru layer provided thereunder.
 12. The method for fabricating adielectric element according to claim 11, wherein the conductive layer(lower electrode) in the step (I) is a Pt layer.
 13. The method forfabricating a dielectric element according to claim 12, wherein the Ptlayer is formed by electroplating.
 14. A dielectric element comprisingan Ru layer, a Pt layer, a dielectric layer, an Ru layer, and a Ptlayer, which are sequentially deposited on a substrate.
 15. Thedielectric element according to claim 14, wherein a processing dimensionof the element is 0.5 μm or less.
 16. A method for fabricating adielectric element, comprising: (I) forming an Ru layer on a substrate;(II) forming a photoresist layer on the Ru layer; (III) selectivelyexposing the photoresist layer, and forming a photoresist pattern as amask on the Ru layer; (IV) forming a Pt layer, which is to be a lowerelectrode, on an exposed or unmasked area of the Ru layer byelectroplating using a Pt plating solution utilizing the Ru layer as anelectroplating electrode; (V) removing the photoresist pattern and theRu layer provided thereunder; (VI) forming a dielectric layer on the Ptlayer; (VII) forming an Ru layer on the dielectric layer; (VIII) forminga photoresist layer on the Ru layer; (IX) selectively exposing thephotoresist layer, and forming a photoresist pattern as a mask on the Rulayer; (X) forming a Pt layer, which is to be an upper electrode, on anexposed or unmasked area of the Ru layer by electroplating using a Ptplating solution utilizing the Ru layer as an electroplating electrode;and (XI) removing the photoresist pattern and the Ru layer providedthereunder.